JP3763105B2 - Two-chamber pacing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to cardiac pacing systems and methods, and more particularly to a dual chamber cardiac pacing system and method for delivering ventricular pacing pulses synchronized to atrial signals for patients with hypertrophic obstructive cardiomyopathy.
[0002]
[Prior art and problems to be solved by the invention]
Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by a constricted left ventricular outflow tract (LVOT) that causes a significant increase in the pressure gradient under the aorta. Stenotic LVOT is caused by an increase in the thickness of the ventricular septum and impedes blood flow during a systole period or at the time of cardiac blood extraction.
[0003]
In some cases, symptoms in HOCM patients can be improved using standard drug therapy. However, the literature points out that there are problems with the drugs used for this treatment. It may also be treated with surgical involvement, such as septal resection or mitral valve replacement. However, these surgical treatments have a high mortality rate and have not been able to change the history of this type of disease. “Permanent Pacing As Treatment For Hypertrophic Cardiomyopathy” (see Kenneth M. McDonald et al., American Journal of Cardiology, Vol. 68, pages 108-110, published in July 1991).
[0004]
It is known in the literature that treatment with dual chamber cardiac pacing is effective in saving patients from suffering from HOCM. Modern multimode dual chamber cardiac pacemakers aim to maintain atrioventricular synchrony of the heart that is damaged or dysfunctional and unable to become autonomous. For example, a DDD pacemaker has electrical connections to the atria and ventricles, senses electrical signals in both chambers of the patient's heart, delivers atrial pacing stimuli when there is no signal indicative of natural atrial contraction, Ventricular pacing stimuli are provided when there is no signal indicative of ventricular contraction. This type of dual chamber pacemaker maintains ventricular synchrony of the heart by delivering ventricular pacing pulses at controlled atrioventricular intervals after each atrial event.
[0005]
Studies have shown that patients suffering from HOCM may be saved in a specific mode of two-chamber pacing, in which ventricular pacing pulses are sensed or paced atrial depolarization and delivered synchronously. It is believed that pacing the right ventricular apex before spontaneous atrioventricular heart block conduction activates the left ventricle alters the activity pattern of the ventricular septum. This reduces leftward movement of the septum, thereby reducing LVOT occlusion and subaortic pressure gradient.
[0006]
There is literature that highlights the importance of achieving ventricular capture and uniformly confirms the possible benefits of synchronized AV pacing for HOCM patients. Inducing “complete ventricular capture” is important to obtain the septal motion described above, but selecting the longest atrioventricular delay to achieve complete ventricular capture will reduce the atrial contribution to ventricular filling. It is important to maximize. See U.S. Application No. 08 / 214,933 (Filing Date March 17, 1994, Title of Methodology For Dual Chamber Cardiac Pacing). The delivered pacing pulse should provide “pre-excitation”, ie depolarization of the ventricular apex in front of the septum. It has been generally recognized that this altered septal contraction pattern is important not only for optimal left ventricular filling, but also for this mode of pacemaker therapy. Also, supplying such synchronized atrioventricular pacing to HOCM patients seems to establish a long-term effect, i.e., an effect that remains after pacing pauses. This is because such atrioventricular pacing causes a decrease in LVOT obstruction that persists in sinus rhythm after pacing cessation.
[0007]
The literature indicates that the AV replacement systolic interval should be set to the longest duration that maintains ventricular capture at different exercise levels. See the above McDonald paper. It has been pointed out that the AV replacement contraction interval allowed for maximum premature ventricular excitation by pacing pulses can be selected by determining the AV replacement contraction interval that results in the widest pacing QRS complex duration. . Vol. 8 Circulation of such Fananapazir, No. 6, June 1992, reference is made to the "Impact of Dual Chamber Permanent Pacing in Patients With Obstructive Hypertrophic Cardiomyopathy With Symptoms Refractoryto Verapamil and B-Adrenergic Blocker Therapy" by the pp. 2149-2161 I want.
[0008]
Pacemakers are known that periodically check to determine the intrinsic AV conduction time (AVC) value and subtract the ventricular sensing offset interval (VSO) therefrom to obtain an AV replacement contraction interval. After the ventricular depolarization waveform resulting from complete capture is found and recorded for comparison, the AV supplemental contraction interval is set to an extended value depending on the outcome of one or more ventricular sensing events. The AVC value is determined as the time difference between the atrial event and the sensed R wave. After this, the pacemaker AV supplementary contraction interval is further reduced until the pacemaker finds an R-wave with a waveform indicating good capture. The difference between the AVC and AV capture values is USO, after which the pacemaker sets AV = AVC-VSO.
[0009]
The prior art for synchronous pacing of HOCM patients recognizes the need to periodically evaluate atrioventricular delay or AV replacement contraction intervals. The patient's spontaneous atrioventricular heart block conduction time varies with heart rate, eg, when changing from rest to exercise. In addition, concurrent drug treatments such as beta blockers may alter AV conduction time and require updated assessments for atrioventricular delay. To ensure complete ventricular capture, if the atrioventricular delay is adjusted to a too short value, the atrial contribution to ventricular filling is compromised. However, if the AV replacement systolic interval is adjusted to a too large value, ventricular capture may be impaired and ventricular pacing may be lost or ventricular pacing may not contribute to the most desirable reduction in LVOT obstruction. Absent. Therefore, in this treatment, the development of a natural heartbeat that results in an AV delay that is too long to be effected by the delivered ventricular pacing pulse in order to be able to continuously adjust the AV replacement contraction interval. It is important to ensure that the intrinsic AV conduction time is safely positioned at a short value while avoiding.
[0010]
[Means for Solving the Problems]
The present invention provides an apparatus and method that utilizes ventricular fusion contraction detection as the basis for an automatic AV delay algorithm for dual chamber pacing therapy in HOCM patients. When the atrioventricular interval of a dual chamber pacemaker is set to approximately the same value as the natural conduction time, ventricular pacing pulses occur simultaneously with the natural R wave, resulting in a condition known as “fusion”. This condition is not necessarily harmful, but has been viewed as undesirable because the energy of the pacing pulse is wasted in the heart tissue and does not respond to the pacing pulse. When fusion occurs, the shape of the resulting R wave is different from the result of maximum capture with the natural QRS complex waveform and the supplied pacing pulses. This form change includes a change in the frequency content of the R wave and the T wave. Also, the amplitude of the T wave induced by the pacing pulse decreases when fusion is achieved. The amplitude of the T wave after natural ventricular depolarization (VS) is too low to be sensed by a T wave sense amplifier. Thus, if a continuous ventricular stimulation pulse is supplied with an atrioventricular delay that increases continuously towards the intrinsic atrioventricular interval, a change in T-wave morphology, particularly a decrease in T-wave amplitude, may occur. Can be observed as it approaches the value causing fusion shrinkage. Accordingly, a pacemaker is provided that monitors the T-wave response as an indicator of when and as the atrioventricular delay corresponding to the intrinsic PR interval (AVC) approximately offset minus approaches the value at which fusion occurs (AVfus). be able to. The pacemaker uses this information to adjust the pacemaker AV supplementary systolic interval (AVesc) to deliver a ventricular pacing pulse shortly before fusion occurs. Ventricular pacing pulses appearing during a fusion beat do not provide maximum capture and it is desirable to use the start of fusion as the dynamic maximum range of AVesc used by the pacemaker.
[0009]
Thus, in the same method as the pacemaker device of the present invention, the pacemaker uses an algorithm that adjusts the atrioventricular delay within the maximum range of AVfus to maximize complete ventricular capture. In order to adapt AVesc to maintain optimal early excitement, the pacemaker is programmed to increase atrioventricular delay until the onset of ventricular fusion is detected. Following ventricular fusion detection or the start of fusion, AVesc is immediately reduced to a value that guarantees complete ventricular capture, and subsequently AVesc is increased with each pulse until ventricular fusion is detected again. By using ventricular fusion as a control variable to tune AVesc, continuous, automatic adjustment of AVesc is provided, with continuous capture by pacing pulses other than in the case of almost complete fusion initiation capture, Retain AVesc within a dynamic range less than intrinsic atrioventricular conduction. In this device, the pacemaker of the present invention provides an optimal atrioventricular delay for ventricular filling, while eliminating the need to suffer from a sensed ventricular event or multiple fusion contractions, thereby Maximize the effectiveness of pacing therapy for HOCM patients.
[0010]
Preferably, the driving variable for adjusting AVesc is T-wave detection. The device of the present invention monitors the T-wave amplitude, determines whether this T-wave amplitude falls by an absolute or relative amount sufficient to indicate a T-wave detection failure, and indicates fusion or fusion start To do. The pacemaker first responds to establish an aggressive decrease in AVesc, for example 20 ms, and then executes a program to increment AVesc during successive pacemaker cycles, towards the AVfus prior measured value. To return. Preferably, as AVesc approaches the pre-determined value of AVfus, AVesc is increased in shorter increments, thereby maximizing the number of pacing pulses delivered before the end of the intrinsic atrioventricular conduction period.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the exterior structure of a dual chamber pacemaker 6 having a hermetically sealed housing 8 and generally made of a biocompatible metal such as titanium. A connector block assembly 12 is attached to the top of the cover 8 and receives electrical connectors located at the proximal ends of the leads 14 and 16. Lead 16 is an atrial pacing lead carrying two electrodes 20 and 21. Electrodes 20 and 21 are used to sense atrial depolarization and deliver atrial pacing pulses. An atrial pacing pulse is delivered between electrode 20 and electrode 21 or between electrode 21 of pacemaker 6 and housing 8. Sensing of atrial depolarization can also occur between electrode 20 and electrode 21 or between either electrode 20 and 21 and housing 8 of pacemaker 6.
[0012]
Similarly, lead 14 represents a ventricular bipolar pacing lead carrying two electrodes 28 and 29. As described above in connection with atrial lead 16, electrodes 28, 29 are used for sensing and pace the ventricles. Ventricular pacing is performed between electrodes 29 and 28 or between electrode 29 of pacemaker 6 and conductive housing 8. Ventricular signal sensing and depolarization (QRS group wave) and repolarization (T-wave) can occur between electrodes 29 and 28 or between electrodes 29 and 28 and housing 8 of pacemaker 6.
[0013]
As discussed in this application, the preferred example of pacemaker 6 operates in DDD or DDDR pacing mode, pacing pulses are sent to the atria and ventricles, and atrial and ventricular depolarizations occur in the chamber where they are detected: It is effective in suppressing the supply of scheduled pacing pulses. DDDR can be used for patients with drug-induced chronotropic incompetence. The present invention appears to be optimal for pacemakers operating in DDD or DDDR pacing mode. Also, in some patients, devices in VDD or DVI modes that only deliver ventricular pacing pulses that are synchronized only to sensed atrial depolarization, or only deliver atrial pacing pulses based on the patient's specific potential cardiac condition, respectively. It is effective in operating. However, DDD or DDDR mode is the most widely used mode for implementing the present invention.
[0014]
FIG. 2 is a block functional diagram of the pacemaker shown in FIG. 1 as connected to the heart 10. The circuit shown is all located within the conductive housing 8 of the pacemaker. The bipolar leads 14, 16 are then shown as being directly coupled to the circuit. Of course, however, in an actual device, they are coupled by a detachable electrical connector inserted into the connector block 12 shown in FIG.
[0015]
In general, the pacemaker is divided into a microcomputer circuit 302 and a pacing circuit 320. The pulse generation output amplification circuit 340 is not only coupled to the atrial pulse generation output amplification circuit connected to the heart 10 by the atrial electrodes 20, 21 on the lead 16, but also ventricular pulses connected to the heart 10 by the electrodes 29, 28 on the lead 14. Includes generation output amplifier circuit coupling. Similarly, pacing circuit 320 includes atrial and ventricular sense amplifiers in sense amplifier circuit 360. The sense-up circuit 360 is connected to the atrium and ventricle by leads 14 and 16. The ventricular sense amplifier is provided for separating detection and identification of QRS group wave and T wave signals in a known manner. Pulse generation output amplifier circuit 340 and sense amplifier circuit 360 include a pulse generator and a sense amplifier. These are used in commercial cardiac pacemakers. Timing control and other functions within the scope of the pacemaker circuit are provided by a digital controller / timer circuit 300 that includes a timer and a corresponding logic set. The digital controller / timer circuit 330 defines the basic pacing interval of the device. The pacing interval may take the form of an A-A supplementary systolic interval that starts with atrial sensing or pacing and triggers atrial pacing in expiration, or it begins with ventricular sensing or pacing and triggers ventricular pulse pacing with expiration. It can take the form of a V refill contraction interval. As will be described later, similarly, the digital controller / timer circuit 330 defines an AV replenishment contraction interval (AVesc). The specific value of the specified interval is controlled by the microcomputer circuit 302 via the data and control bus 306. The sensed atrial depolarization is communicated to the digital controller / timer circuit 330 via the A event line 352 and the ventricular depolarization (QRS group wave) is communicated to the digital controller / timer circuit 330 via the V event line 354. Ventricular repolarization (T wave) is then transmitted to circuit 330 on via T wave line 353. To trigger the generation of a ventricular pacing pulse, the digital controller / timer circuit 330 generates a trigger signal on the V trigger line 342. Similarly, to trigger an atrial pacing pulse, the digital controller / timer circuit 330 generates a trigger pulse on the A trigger line 344.
[0016]
The digital controller / timer circuit 330 also defines a time interval to control the operation of the sense amplifier in the sense amplifier circuit 360. In general, the digital controller / timer circuit 330 determines an atrial blanking interval that disables atrial sensing after supplying an atrial pacing pulse, and a ventricular blanking interval that disables ventricular sensing after supplying an atrial and ventricular pacing pulse. Stipulate. The digital controller / timer circuit 330 also defines an atrial refractory period when atrial sensing is not available. This refractory period extends from the beginning of the AV supplementary contraction interval following a sensed or paced atrial depolarization to a predetermined time after pre-sensing of ventricular depolarization or delivery of a ventricular pacing pulse. Similarly, the digital controller / timer circuit 330 defines the delivery of ventricular refractory periods or ventricular pacing pulses after ventricular sensing. It is generally the shorter part of the atrial refractory period or pacing following ventricular sensing. The digital controller / timer circuit 330 also controls sensitivity setting of the sense amplifier 360 by the sensitivity adjustment circuit 350. This sensitivity adjustment circuit can be used to distinguish QRS group waves from T waves. See U.S. Pat. No. 4,665,919 in this regard.
[0017]
In the embodiment shown in FIG. 2, to enable the delivery of rate-responsive pacing, the pacemaker includes a piezoelectric sensor 316 that monitors the patient's body movements and provides a prescribed pacing rate (A-A supplemental contraction interval or (VV supplemental contraction interval) increases with increased demand for oxidized blood. The sensor 316 generates an electrical signal in accordance with the sensed body movement. It was processed by the body movement circuit 322 and supplied to the digital controller / timer circuit 330. The sensor 316 corresponding to the body motion circuit 332 corresponds to the circuit disclosed in US Pat. No. 5,052,388 to Anderson et al. And US Pat. No. 4,428,378 to Betzold et al. Similarly, the present invention is implemented in connection with all other types of sensors known for use in providing rate responsive pacing capabilities such as oxygen sensors, pressure sensors, pH sensors, and respiratory sensors. Can do. The QT time can also be used as a parameter indicating the rate when no sensor is required. Similarly, the present invention may be practiced with non-rate responsive pacemakers.
[0018]
Transmission between the external programmer 9 shown in FIG. 2 is made by an antenna 334 and a corresponding RF transceiver 332. The RF transceiver 332 demodulates the received downlink telemetry and transmits the uplink telemetry. While battery 318 supplies power, crystal oscillator circuit 338 provides a clock that takes the basic timing of the circuit. The power-on reset circuit 336 is responsive to the initial connection of the circuit to the battery to define the initial operating conditions, and similarly resets the operating state of the device in response to detection of a low battery state. Reference voltage and bias circuit 326 generates a fixed reference voltage and current for the analog circuitry within pacing circuit 320. The AD converter ADC and multiplexer circuit 328 digitize the analog signal and voltage and provide real-time telemetry of the heart signal from the sense amplifier 360 for uplink transmission through the RF transceiver circuit 332. Reference voltage and bias circuit 326, ADC and multiplexer 328, power on reset circuit (POR) 336, and crystal oscillator circuit 338 are those used in commercially available implantable cardiac pacemakers.
[0019]
The microcomputer circuit 302 specifies which timing intervals are employed to control the operable functions of the digital controller / timer 330 and controls the duration of the various timing intervals via the data and control bus 306. . The microcomputer circuit 302 includes a system clock 308 corresponding to the microprocessor 304 and board mounted RAM circuits 310 and 312. In addition, the microcomputer circuit 302 includes a separate RAM / ROM chip 314. Microprocessor 304 normally operates in a driven interrupt, power saving mode, and is activated in response to a prescribed interrupt event to sense not only the delivery of atrial and ventricular pacing pulses, but also atrial and ventricular depolarization. In addition, if the device operates as a rate-responsive pacemaker, a timed interrupt, such as an interrupt every cycle or every 2 seconds, is provided to allow the microprocessor to analyze the sensor data, Update the device's basic rate period (AA or V-V). In addition, the microprocessor 304 preferably serves to define a variable AV supplemental contraction interval and an atrial, ventricular refractory period that decreases in duration as well as decreases in duration of the basic rate cycle. In particular, the microprocessor is used to execute the routines shown in FIGS.
[0020]
The circuit of FIG. 2 is exemplary and corresponds to the general functional configuration of most commercially available microprocessor controlled cardiac pacemakers. The present invention can easily implement the software stored in ROM 312 of microprocessor circuit 302 using the basic hardware of an existing microprocessor controlled dual chamber pacemaker. However, the present invention can be implemented by a custom integrated circuit or a combination of hardware and software.
[0021]
Referring to FIGS. 3-5, there is shown a general flow chart of the processing steps taken by the pacemaker of the present invention to perform the method of adjusting AVesc for optimal synchronized pacing of the ventricle to provide HOCM therapy. The steps of this flowchart are executed by the microcomputer circuit 302. This is a flow chart that briefly describes the steps involved in controlling AVesc for HOCM treatment and does not include many other steps and responses that occur during each cycle of a typical dual chamber pacemaker . In the logic shown in FIGS. 3-5, atrial depolarization in which the intrinsic AV conduction time after an atrial pacing pulse is sensed is described as “atrial sensing offset” or ASO in US application Ser. No. 08 / 214,933. It can be seen that the amount exceeds the specified amount. AVesc following atrial pacing is defined as PAV, AVesc following atrial sensing is defined as SAV, and PAV = SAV + ASO. On the other hand, although the present invention is shown to generate separate values for SAV and PAV, the present invention is not so limited.
[0022]
At block 401, the routine of FIGS. 3-5 is waiting for what appears to be an atrial event. When an event occurs, the routine goes to block 402 to determine if an atrial supplementary systolic interval (Aesc) timeout has been present. If yes, this indicates that atrial pacing (AP) should be delivered and is done at block 404. Then, at block 406, the routine goes to block 412 to set AVesc in the PAV and to start the AVesc timeout. Returning to block 402, if there is no Aesc timeout, the pacemaker proceeds to block 408 to determine if there was an initial ventricular sensing (VS). If yes, the routine branches to block 409, resets the timing appropriately, and then returns to block 401. However, usually at block 408, if the event is not VS, it means an atrial sense (AS), and the routine proceeds to block 410 and sets AVesc to the current value of SAV. After this, the routine goes to block 412 to start a timeout for the atrial supplementary systolic interval Aesc and a timeout for the AV supplemental systolic interval AVesc (SAV or PAV). Then, at block 414, the pacemaker waits for the next event (usually one ventricular event). At block 415, the pacemaker responds to the event with an initial determination of whether the event was an Avesc timeout. If NO, it means that ventricular sensing was present and the pacemaker proceeds to block 417 and resets PAV and SAV to shorter values that ensure capture by the next ventricular pacing pulse. For example, each of these values can be decremented by 50 milliseconds to ensure that a subsequent timeout of AVesc occurs early enough to ensure ventricular capture. However, the algorithm described below is intended to avoid the occurrence of VS, and pacemakers should rarely take this path.
[0023]
If there is an AVesc timeout at block 415, the pacemaker proceeds to block 418 to supply V pacing. The routine then proceeds to block 420 to monitor atrioventricular data. As mentioned above, this data is preferably in T-wave amplitude or T-wave form. Having obtained this data, the pacemaker adjusts the PAV and SAV values at block 422 to optimize the resulting early excitement according to a predetermined algorithm for maximizing AVesc. After this, the routine returns to block 401 and waits for the next atrial or ventricular event (PVC).
[0024]
Although the preferred embodiment monitors atrioventricular data and adjusts AVesc for each pacemaker cycle, in the present invention these steps can be performed on other periodic or programmed basis.
[0025]
Referring to FIG. 6, a simple flowchart of the steps performed corresponding to block 422 is shown. Block 422 includes a survey or scan to move AVesc towards the value corresponding to the fusion. Based on the monitored data, the pacemaker determines whether the AV should be adjusted at block 424. If yes. If so, the routine adjusts PAV and SAV as indicated by block 425. However, if NO, the adjustment is appropriate and the routine goes to block 426. The pacemaker then decides whether the program is set up to do an atrioventricular study or scan. If no, the routine ends. However, if search is programmed, go to block 427 and adjust AVesc according to a predetermined survey routine. The search routine is aimed at directing Avesc to the fusion value. The survey routine can also be a programmed routine. For example, one of the routines is shown in FIGS. 5B, 5C, 5D, 5E.
[0026]
Referring to FIG. 5, a simple flowchart summarizing a simple routine for adjusting AV as well as scanning and searching is shown. At block 429, the routine determines whether V sensing was present. If yes, the routine branches to block 430 where the AV is decremented by Δ1, eg, 25 or 50 milliseconds. However, if there is no V sense, the routine goes to block 432 and determines whether the monitor data indicates whether to adjust. If yes, the routine goes to block 433 and decrements AV by Δ2 (equal to or less than Δ1). If the data does not indicate adjustment at block 432, the routine goes to block 434 to perform a simple scan step. That is, AV is incremented by Δ3 (preferably a small value such as 5 milliseconds).
[0027]
Referring to FIG. 6, there is shown a more detailed flowchart of the apparatus and method of the present invention corresponding to blocks 420, 422 of the first embodiment of FIGS. In FIG. 6, for the sake of simplicity, only the adjustment of AVesc is shown without distinguishing between SAV and PAV. At block 435, the pacemaker monitors the ventricular sense amplifier response to see if a T wave has been detected on line 353. If NO, i.e. there is a significant drop in T-wave amplitude, this indicates that the supplied VP has occurred as a result of a fusion contraction, or at least an approximate fusion or similar fusion beat has occurred. . In this case, the routine branches to block 440 and sets the variable designated AVfu to the current value of AVesc that led to the fusion contraction. If a T wave is detected at block 435, the routine proceeds to block 437 and determines the amplitude of the T wave (Tamp) and compares it to the previous value of Tamp. The sensitivity of current T-wave sense amplifiers, such as those used in Q-T rate response pacemakers made by Vitronon Medical, can be programmed within the range of 0.5-3.0 mV, the comparison is 0.25 mV Can be made. At block 438, the pacemaker compares the changes in Tamp to see if there was a decrement that exceeded a predetermined threshold Th. This comparison can be made because even if a T wave is still detected, a sudden and significant drop in the T wave amplitude can reliably indicate the start of fusion. According to this embodiment of the invention, the fusion criterion is either one decrease in T-wave sensing or a decrease in T-wave amplitude above Th (eg, at least 25%). If such a rapid drop occurs, the pacemaker adjusts the value of AVfus at block 440. It then decrements AVesc at block 442. The decrement value can be a fixed program value, but more suitably is a value calculated by a pacemaker according to AVfus and its history, as discussed in more detail below. However, it is desirable to adjust AVesc as the first function of AVfus (f1 (AVfus)), as generally indicated by block 442. Returning to block 438, the routine branches to block 443 if there is no suddenly falling T-wave amplitude. AVesc is incremented to take a value toward the value corresponding to the fusion (AVfus). As will be discussed below, the incremental amount may even vary according to different criteria. As shown in FIG. 6, AVesc is generally incremented according to the second function of AVfus (f2 (AVfus)). Thereafter, at block 445, data regarding the current scan of Vesc is stored for use in changing f1 and / or f2, as described below in connection with FIGS.
[0028]
As mentioned above, characteristics of T-waves other than amplitude can be used to detect the start of fusion. When AVesc approaches AVfus, the frequency characteristics and form of the T wave change. Therefore, the present invention can be implemented by monitoring one or more characteristics of the T wave, such as duration or slope. Similarly, the stimulus and R wave morphology for the induced R wave duration changes significantly in fusion and can be used as a control variable.
[0029]
Referring to FIG. 7A, based on the detection of a sensed ventricular event, the results of a pacemaker algorithm that does not take advantage of the present invention are shown, and the intrinsic PR until obtaining a sensed ventricular signal (VS). This algorithm throughout the interval scans for AV delay. Thereafter, the atrioventricular delay is decremented and the investigation is repeated. As shown, this occurs as a result of a periodic decrease in capture at points where the HOCM patient does not benefit from premature excitement due to pacing pulses. In contrast, FIG. 7B shows a scanning algorithm according to the present invention, in which the pacemaker detects fusion with an atrioventricular delay that is slightly shorter than the intrinsic PR interval. FIG. 7 (B) shows a relatively constant intrinsic PR interval, each time the fusion is detected by the absence of waves or a significant decrease, and the algorithm is AV in a predetermined amount, eg 20 ms. Indicates the situation of decrementing. In this embodiment, at block 442, AVesc is decremented by a predetermined amount after fusion contraction. This predetermined amount can be a fixedly programmed amount or a function of the AV delay, i.e., AVfus, where fusion is seen. As shown in FIG. 7B, due to the generally constant potential PR interval, the pacemaker is responsible for an initial decrement of 20 ms in block 442 and a fixed increment of 1 ms in block 443. In addition, the atrioventricular delay is incremented through N cycles (eg, N = 20) before detecting fusion. However, it must be understood that the intrinsic PR interval does not remain constant and varies for exercise and other reasons. For example, FIG. 7C shows a situation with intrinsic spacing, eg shortening or decreasing during exercise. FIG. 7D shows a situation with an intrinsic PR interval that increases after, for example, a pause in exercise.
[0030]
In one embodiment of the invention, the pacemaker is programmed to count the scan period, ie, count N, in which AVesc is incremented as an action in block 445. If N remains between 75% and 125% of its nominal value (eg, between 15 and 25), the potential PR interval is considered constant. If the potential PR interval is reduced as illustrated in FIG. 7C, the number of pulses between the two fusion detections (N) is reduced. For example, if N does not drop that much below 75% (eg, 15) of its nominal value (No), a relatively aggressive shortening and pacemaker algorithm will maintain a constant bunch over a predetermined number of pulses. Shows that it responds by maintaining room delay (AVEsc). In this case, the formula for incrementing AVesc keeps it constant. That is, f2 (AVfus) = K. Usually in this situation, shortening the patient's PR interval causes fusion detection again after at most 20 pulses. However, if no fusion is detected after a predetermined number of pulses, straight AV (eg, 1 ms / beat) delays and restarts the increment.
[0031]
Referring to FIG. 7 (D, the patient's intrinsic PR interval is shown to be longer during recovery from exercise, and it can be seen that the number of cycles N between the two fusion contractions is increased. According to another embodiment, when N exceeds a fixed percentage of reference N (eg, N ≧ 1.25N0), the algorithm increases the step size of the atrioventricular increment (eg, from 1 ms / beat to 2). The algorithm recovers to a smaller step size increment when it is detected that N again falls within 25% of N0, so the counting period technique during fusion contraction tracks AVfus. However, there is a specific embodiment where the f2 function is adjusted to increment AVesc at block 443.
[0032]
In the present invention, other alternative programs for adjusting AVesc to maximize atrioventricular delay for optimal filling, while avoiding making AVesc too long so that capture is occasionally missed Is possible. The purpose of any alternative algorithm is to maintain optimal atrioventricular delay for blood circulation while the patient's potential rate and intrinsic PR interval are changing, while maximizing It is to ensure capture. FIG. 7E shows, in an alternative algorithm example, a different f1 that decrements AVesc following the fusion and a different f2 that increments AVfus after the fusion. In this example, the f1 function provides an automatic step reduction of AVec upon detection of fusion. However, this step size reduction can be made smaller if the patient's potential PR interval is approximately constant. Similarly, the increment of AVec in the subsequent period can be made smaller. For example, after fusion detection following an N-beat scan and 0.75N0 ≦ N ≦ 1.25N0, AVesc is decremented by 10 milliseconds instead of 20 milliseconds at block 442, after which AVesc is 50 of the following N pulses. It is kept constant over% and incremented with a period of 1 millisecond. This is a result of an approximately constant value of N during fusion contraction, with an average AV delay longer and closer than AVfus.
[0033]
It should be noted that the terms “fusion” and “fusion contraction” used in the above description include situations where the evoked response, including T-wave amplitude, changes sufficiently to exhibit some characteristics of fusion or approximate fusion.
[0034]
【The invention's effect】
The present invention provides an improved system and method for dual chamber pacing treatment of HOCM patients. The present invention includes an improved aspect of detecting the maximum range of the atrioventricular interval, and the pacemaker paces to optimize the patient's heart and efficient two-chamber hemodynamically complete capture. The present invention includes a novel method for discovering when a pacemaker AV delay corresponds to a fusion contraction, thereby accurately detecting an atrioventricular delay that does not suffer from a pacemaker cycle without the capture for delivery of a pacing pulse. Detect the maximum allowable range for. With the fact that there is no capture for delivery of pacing pulses, the technique of monitoring the sensed T-wave amplitude allows the present invention to determine when the prolonged atrioventricular delay reaches a value corresponding to the onset of fusion. Provide ample safety to detect and prevent loss of capture. The present invention provides an algorithm for optimizing the range of change in AVesc as a function of the detected fusion interval AVfus used as the maximum of the pacemaker AVesc range.
[Brief description of the drawings]
FIG. 1 is a perspective view of a pacemaker system of the present invention showing an implantable pacemaker connected to the heart of a patient.
FIG. 2 is a block diagram of the main functional components of the pacemaker system and the method of the present invention.
FIG. 3 is a flowchart illustrating steps during synchronous pacing in accordance with the present invention.
FIG. 4 is a simplified flowchart showing a survey step.
FIG. 5 is a simplified flowchart illustrating a special routine for adjusting search and AVesc.
FIG. 6 is a flow chart for performing an adjustment step according to a preferred embodiment of the present invention.
FIG. 7 is a timing diagram showing the results of an algorithm for AVesc control based on detection of ventricular sensing.
[Explanation of symbols]
6 Two-chamber pacemaker
8 Housing
9 Programmer
10 heart
12 Connector block assembly
14,16 lead
20, 21, 28, 29 electrodes
302 Microcomputer circuit
304 microprocessor
308 System clock
310, 312 Board mounted RAM circuit
314 RAM / ROM chip
316 Piezoelectric sensor
320 Pacing circuit
322 Body movement circuit
326 Reference voltage and bias circuit
328 ADC and multiplexer
330 Digital Controller / Timer Circuit
332 RF transceiver
334 antenna
336 Power-on reset circuit
338 Crystal oscillation circuit
340 Pulse generation output amplifier circuit
350 Sensitivity adjustment circuit
360 sense amplifier circuit

Claims (11)

An atrial sensing means (16, 360, 352) for sensing a patient's atrial signal; a ventricular sensing means (14 , 360 , 354) for sensing a patient's ventricular signal; and a ventricle that produces a ventricular pacing pulse for delivery to the right ventricle of the patient. pacing means (340,342,14) and controlling the pacing means generates a ventricular pacing pulse at the sensed subsequently controlled AV escape interval in the atrial signal from the synchronization control means for supplying (330,302) In the two-chamber pacemaker system in which the synchronous control means has AVesc means (406, 410) for setting the AV supplementary contraction interval, the occurrence of the fusion contraction and the AV supplementary contraction interval corresponding to the detected fusion contraction . Fusion means (420, 435, 437, 438, 440) for detecting AVfus value , and AVf pacing pulses including program means (422, 442, 443) for varying the AV supplementary contraction interval in order to maintain the AV supplementary contraction interval set by the AVesc means within a narrow range of values not greater than the us value Is a two-chamber pacemaker system that supplies an AV replenishment contraction interval that is less than or equal to the AVfus value and in the vicinity thereof , wherein the fusion means detects a T wave (360, 353) after delivery of a ventricular pacing pulse And a first determining means (435) for determining fusion contraction when no T wave is detected after the delivered ventricular pacing pulse . Atrial sensing means (16, 360, 352) for sensing the patient's atrial signal, ventricular sensing means (14, 360, 354) for sensing the patient's ventricular signal, and a ventricle that generates a ventricular pacing pulse to supply to the right ventricle of the patient. From the pacing means (340, 342, 14) and the synchronous control means (330, 302) which controls the pacing means and generates and delivers ventricular pacing pulses at a controlled AV supplementary contraction interval following the sensed atrial signal In the two-chamber pacemaker system in which the synchronous control means has AVesc means (406, 410) for setting the AV supplementary contraction interval, the occurrence of the fusion contraction and the AV supplementary contraction interval corresponding to the detected fusion contraction. Fusion means (420, 435, 437, 438, 440) for detecting AVfus value, and AVf program means (422, 442, 443) for varying said AV escape interval to within a narrow range of s is not greater than value the value to maintain said AV escape interval said AVesc means sets include, pacing pulses Is a two-chamber pacemaker system that supplies an AV replenishment contraction interval equal to or less than the AVfus value, wherein the fusion means detects a T wave in response to the supplied ventricular pacing pulse. (360, 353) and amplitude means (437) for determining the amplitude of the detected T-wave and second means (438) for determining fusion contraction as a function of the detected T-wave amplitude. Features a dual chamber pacemaker system. Atrial sensing means (16, 360, 352) for sensing the patient's atrial signal, ventricular sensing means (14, 360, 354) for sensing the patient's ventricular signal, and a ventricle that generates a ventricular pacing pulse to supply to the right ventricle of the patient. From the pacing means (340, 342, 14) and the synchronous control means (330, 302) which controls the pacing means and generates and delivers ventricular pacing pulses at a controlled AV supplementary contraction interval following the sensed atrial signal In the two-chamber pacemaker system in which the synchronous control means has AVesc means (406, 410) for setting the AV supplementary contraction interval, the occurrence of the fusion contraction and the AV supplementary contraction interval corresponding to the detected fusion contraction. Fusion means (420, 435, 437, 438, 440) for detecting AVfus value, and AVf In a narrow range of s is not greater than the value a value includes program means (422,442,443) for varying said AV escape interval to maintain said AV escape interval said AVesc means is set, the pacing pulses Is a two-chamber pacemaker system that supplies a value less than or equal to the AVfus value and an AV replenishment contraction interval in the vicinity thereof, monitor means for monitoring T-wave amplitude (435, 437), and when the T-wave amplitude is fused A two-chamber pacemaker system comprising an evaluation means (432) for evaluating whether or not the information is indicated . Ventricular produce a ventricular pacing pulse you supplied to the patient's atrial sense means (16,360,352) for sensing atrial signals, ventricular sense means for sensing ventricular signals of a patient (14,360,354) of the patient the right ventricle From the pacing means (340, 342, 14) and the synchronous control means (330, 302) which controls the pacing means and generates and delivers ventricular pacing pulses at a controlled AV supplementary contraction interval following the sensed atrial signal In the two-chamber pacemaker system in which the synchronous control means has AVesc means (406, 410) for setting the AV supplementary contraction interval, the occurrence of the fusion contraction and the AV supplementary contraction interval corresponding to the detected fusion contraction. Fusion means for detecting AVfu value (420, 435, 437, 438, 440), and AVfu Includes program means (422,442,443) for varying said AV escape interval to maintain said AV escape interval said AVesc means sets within a narrower range of not greater than the value, the pacing pulses a dual chamber pacemaker system for supplying at a V escape interval of the AVfus value: value less and its vicinity, monitoring means (435, 437) for monitoring T-wave morphology and the T-wave morphology occurrence of at fusion A two-chamber pacemaker system comprising an evaluation means (432, 445) for evaluating whether or not the information is indicated . Atrial sensing means (16, 360, 352) for sensing a patient's atrial signal, ventricular sensing means (14, 360, 354) for sensing a patient's ventricular signal, and ventricular pacing to produce a ventricular pacing pulse to be delivered to the patient's right ventricle. Means (340, 342, 14) and synchronous control means (330, 302) for controlling the pacing means and generating and supplying ventricular pacing pulses at a controlled AV supplementary contraction interval following the sensed atrial signal. In the two-chamber pacemaker system, in which the synchronous control means has AVesc means (406, 410) for setting the AV replenishment contraction interval, AVfusion of the AV replenishment contraction interval corresponding to the occurrence of fusion contraction and the detected fusion contraction Fusion means for detecting values (420, 435, 437, 438, 440), and AVfu Includes program means (422,442,443) for varying said AV escape interval to maintain said AV escape interval said AVesc means sets within a narrower range of not greater than the value, the pacing pulses A two-chamber pacemaker system that supplies an AV replacement contraction interval that is less than or equal to the AVfus value and that is in the vicinity thereof, wherein the program means determines a paced ventricular pulse rate during fusion contraction, and a function of the pulse rate the pacemaker system characterized in including that the means (44 5) that adjust the AV escape interval (442 and 443) as. 6. A dual chamber pacemaker system according to any of claims 1 to 5, wherein said program means (442) comprises decrement means for decrementing said AV supplementary systolic interval for the next ventricular pacing pulse after a detected fusion contraction . 7. The dual chamber pacemaker system of claim 6, wherein said program means comprises means (434, 443) for incrementing said AV supplemental contraction interval by a fixed increment after said next ventricular pacing pulse. The program means varies the AV replenishment contraction interval to enable detection of fusion contraction without extending the AV replenishment contraction interval to a value greater than the AVfus value, and sets the AV replenishment contraction interval (438). 6. A dual chamber pacemaker system according to any of claims 1 to 5 , wherein ventricular sensing prior to timeout is avoided . The program means includes storage means (4 40 ) for storing the AVfus value and means (442, 443) for varying the AV supplementary contraction interval as a function of the stored AVfus value . Any two-chamber pacemaker system. Said program means may be any dual chamber pacemaker 5 means for varying said AV escape interval as a function of the a and the AVfus value range falls below the AVfus values (442, 443) from including claim 1 system. Said program means, of any one of claims 1 pacing pulses supplied comprises means (44 2) for decrementing said AV escape interval for at least the next pacemaker cycle after finding that caused the fusion 5 Two-chamber pacemaker system.

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